Boosting the dark matter signal with Coulomb resonances. (arXiv:1903.00013v2 [hep-ph] UPDATED)
<a href="http://arxiv.org/find/hep-ph/1/au:+Mahbubani_R/0/1/0/all/0/1">Rakhi Mahbubani</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Mimouni_K/0/1/0/all/0/1">Kin Mimouni</a>
We show that the presence of nearby Coulombic resonances at finite energy
could lead to the enhancement of the dark matter annihilation cross section at
specific non-zero velocities correlated with the mass splitting between the
dark matter pair and that of the resonance. If one of these resonant velocities
approximately matches the velocity of dark matter in our local neighbourhood,
we would see this enhancement in existing indirect-detection measurements, such
as the measurements of the continuum photon spectrum made by HESS and
Fermi-LAT. We explore this effect in the context of pure Higgsino and Wino dark
matter with a variable splitting between charged and neutral components,
controlled by the Wilson coefficient of a higher-dimension operator. For
electroweak WIMPs a relevant and appreciable enhancement from Coulomb
resonances requires tuning the charged-neutral splitting to be of order the
Coulomb binding energies. This leads to strong exclusions of Higgsino dark
matter with charged-neutral splittings in the narrow ranges (2, 2.5) and (8.5,
10.5) MeV. In contrast, by decreasing the charged-neutral splitting for the
thermal Wino, we can move the Yukawa resonance away from the thermal relic
mass, decreasing the indirect-detection signal to a level that is compatible
with HESS measurements in the window (25, 35) MeV.
We show that the presence of nearby Coulombic resonances at finite energy
could lead to the enhancement of the dark matter annihilation cross section at
specific non-zero velocities correlated with the mass splitting between the
dark matter pair and that of the resonance. If one of these resonant velocities
approximately matches the velocity of dark matter in our local neighbourhood,
we would see this enhancement in existing indirect-detection measurements, such
as the measurements of the continuum photon spectrum made by HESS and
Fermi-LAT. We explore this effect in the context of pure Higgsino and Wino dark
matter with a variable splitting between charged and neutral components,
controlled by the Wilson coefficient of a higher-dimension operator. For
electroweak WIMPs a relevant and appreciable enhancement from Coulomb
resonances requires tuning the charged-neutral splitting to be of order the
Coulomb binding energies. This leads to strong exclusions of Higgsino dark
matter with charged-neutral splittings in the narrow ranges (2, 2.5) and (8.5,
10.5) MeV. In contrast, by decreasing the charged-neutral splitting for the
thermal Wino, we can move the Yukawa resonance away from the thermal relic
mass, decreasing the indirect-detection signal to a level that is compatible
with HESS measurements in the window (25, 35) MeV.
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